Yes it is Polish medal.
It is "Armed Forces in Service for the Country Medal" (Long Service Medal)
Some history:
Instituted by act of Parliament of May 26, 1951. Conferred to professional officers and NCO's, for long and meritorious service in the armed forces, as well as to civilians working for the armed forces. The medal is conferred in three grades: gold, silver and bronze. The three grades were initially awarded for 15, 10 and 5 years of service. In 1960 the period of service required for the gold and silver medal was extended to 25 and 15 years, while the bronze medal was canceled. It was renewed again in 1968 and the years of service for the upper two grades were shortened to 20 and 10 years respectively. The medals obtained new regulations in 1995 and has since then been awarded by Minister of National Defense. The time of service required to obtain the upper two grades was extended once again to 25 and 15 years.
Badge 1951-1990: gilt, silvered or bronze medal 34 mm of diameter. In the middle there is a non-crowned silver eagle on red enameled background, surroundes by a white enameled circle, circumscribed SILY ZBROJNE W SLUZBIE OJCZYZNY (armed forces in service for the country), and with a small five pointed star at the bottom. The whole is surrounded by a gilt, silver or bronze laurel wreath, superimposed on two crosses swords. At the bottom of the wreath there is a red enameled oval shield with Roman numerals XV, X, V (1951-1960), XXV, XV (1960-1968 ), or XX, X, V (1968-1990). The reverse is plain.